How do I calculate the polyester resin/catalyst ration according to my room temperature? My glassing room is 85 degrees F.
The polyester resin catalyst chart amounts are for room temperature (70 degrees F). There is a note at the bottom to use 1/2 the recommended amount for temperatures above 90F.
Therefore figure at 80 degrees use 3/4 the amount of catalyst on the chart. For laminating in 85F you would use around 60% of the amount catalyst.
It is always better to use less catalyst so the resin cures stronger and not brittle. Plus you have more time to laminate and get all the air bubbles out.